US7872808B2 - Zoom lens system and camera including the same - Google Patents

Zoom lens system and camera including the same Download PDF

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US7872808B2
US7872808B2 US12/476,571 US47657109A US7872808B2 US 7872808 B2 US7872808 B2 US 7872808B2 US 47657109 A US47657109 A US 47657109A US 7872808 B2 US7872808 B2 US 7872808B2
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lens
lens unit
zoom
negative
unit
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US20090296232A1 (en
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Takashi Okada
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Canon Inc
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Canon Inc
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/142—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having two groups only
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/143—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only
    • G02B15/1431—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only the first group being positive
    • G02B15/143105—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having three groups only the first group being positive arranged +-+

Definitions

  • the present invention relates to a zoom lens system and a camera including the same.
  • a camera such as a video camera, a digital still camera, a broadcasting camera, a monitoring camera which use a solid-state image pickup element, or a silver-halide film camera has provided high function and has been small in overall size.
  • a shooting optical system used in the camera is demanded to be a zoom lens system that has short overall length of a lens, small size, a high zoom ratio, and high definition.
  • the shooting optical system is demanded to be a retractable zoom lens system including a configuration for reducing intervals between the respective lens units in non-shooting state to intervals different from those in shooting state and reducing a thickness (length in an optical axis direction) of the entire camera.
  • zoom lens system As a zoom lens system meeting those demands, there is known a zoom lens system that includes, in order from an object side to an image side, first, second, and third lens units respectively having positive, negative, and positive refractive powers and in which the respective lens units move to perform zooming (Japanese Patent Application Laid-Open No. 2005-106925 (corresponding to U.S. Pat. No. 7,123,422)).
  • a positive-lead zoom lens system that includes, in order from an object side to an image side, a lens unit having positive refractive power, a lens unit having negative refractive power, and a rear unit including one or more lens units following those lens units (Japanese Patent Application Laid-Open No. 2005-338740 (corresponding to U.S. Pat. No. 7,283,310) and Japanese Patent Application Laid-Open No. 2007-171371 (corresponding to U.S. Pat. No. 7,319,562)).
  • Japanese Patent Application Laid-Open No. 2005-338740 (corresponding to U.S. Pat. No. 7,283,310) and Japanese Patent Application Laid-Open No. 2007-171371 (corresponding to U.S. Pat. No. 7,319,562) disclose a zoom lens system that includes four lens units respectively having positive, negative, positive, and positive refractive powers in the stated order from an object side to an image side, and in which the respective lens units move to perform zooming.
  • Japanese Patent Application Laid-Open No. 2007-338740 discloses a zoom lens system that includes a second lens unit including two lenses, i.e., a negative lens and a positive lens, and appropriately sets refractive powers of the components to realize a reduction in size of the entire system.
  • translucent ceramics is developed.
  • a shooting optical system employing the translucent ceramics as an optical material is known.
  • the translucent ceramics have a high refractive index compared with optical glass and are excellent in hardness and strength.
  • There is known a camera that realizes a reduction in thickness of an entire lens system making use of this characteristic Japanese Patent Application Laid-Open No. 2006-84887 (corresponding to U.S. Pat. No. 7,407,334)).
  • translucent ceramics is used as a material of a negative lens of a cemented lens, which is formed by bonding a positive lens and the negative lens, to reduce lens thickness and realize a reduction in the entire lens system.
  • optical glass has a characteristic that, as a refractive index increases, an Abbe number decreases and dispersion increases.
  • ceramics has a higher refractive index compared with optical glass having an Abbe number same as that of the ceramics.
  • a first lens unit having positive optical power, a second lens unit having negative optical power, and a rear unit including at least one lens unit are arranged in the stated order from an object side to an image side.
  • at least two lens units move so that intervals between lens units adjacent to each other change.
  • the second lens unit consists of a negative lens component formed of at least one material and a positive lens element.
  • the negative lens component and the positive lens element are arranged in the stated order from the object side to the image side.
  • a refractive index of the at least one material forming the negative lens component with respect to d-line, an Abbe number of the at least one material forming the negative lens component, and a refractive index of a material forming the positive lens element with respect to d-line are appropriately set.
  • FIG. 1 is an optical sectional view in a first embodiment of the present invention.
  • FIG. 2 is a diagram of aberrations at a wide-angle end in the first embodiment.
  • FIG. 3 is a diagram of aberrations in an intermediate zoom position in the first embodiment.
  • FIG. 4 is a diagram of aberrations at a telephoto end in the first embodiment.
  • FIG. 5 is an optical sectional view in a second embodiment of the present invention.
  • FIG. 6 is a diagram of aberrations at a wide-angle end in the second embodiment.
  • FIG. 7 is a diagram of aberrations in an intermediate zoom position in the second embodiment.
  • FIG. 8 is a diagram of aberrations at a telephoto end in the second embodiment.
  • FIG. 9 is an optical sectional view in a third embodiment of the present invention.
  • FIG. 10 is a diagram of aberrations at a wide-angle end in the third embodiment.
  • FIG. 11 is a diagram of aberrations in an intermediate zoom position in the third embodiment.
  • FIG. 12 is a diagram of aberrations at a telephoto end in the third embodiment.
  • FIG. 13 is an optical sectional view in a fourth embodiment of the present invention.
  • FIG. 14 is a diagram of aberrations at a wide-angle end in the fourth embodiment.
  • FIG. 15 is a diagram of aberrations in an intermediate zoom position in the fourth embodiment.
  • FIG. 16 is a diagram of aberrations at a telephoto end in the fourth embodiment.
  • FIG. 17 is an optical sectional view in a fifth embodiment of the present invention.
  • FIG. 18 is a diagram of aberrations at a wide-angle end in the fifth embodiment.
  • FIG. 19 is a diagram of aberrations in an intermediate zoom position in the fifth embodiment.
  • FIG. 20 is a diagram of aberrations at a telephoto end in the fifth embodiment.
  • FIG. 21 is an optical sectional view in a sixth embodiment of the present invention.
  • FIG. 22 is a diagram of aberrations at a wide-angle end in the sixth embodiment.
  • FIG. 23 is a diagram of aberrations in an intermediate zoom position in the sixth embodiment.
  • FIG. 24 is a diagram of aberrations at a telephoto end in the sixth embodiment.
  • FIG. 25 is an optical sectional view in a seventh embodiment of the present invention.
  • FIG. 26 is a diagram of aberrations at a wide-angle end in the seventh embodiment.
  • FIG. 27 is a diagram of aberrations in an intermediate zoom position in the seventh embodiment.
  • FIG. 28 is a diagram of aberrations at a telephoto end in the seventh embodiment.
  • FIG. 29 is an optical sectional view in an eighth embodiment of the present invention.
  • FIG. 30 is a diagram of aberrations at a wide-angle end in the eighth embodiment.
  • FIG. 31 is a diagram of aberrations in an intermediate zoom position in the eighth embodiment.
  • FIG. 32 is a diagram of aberrations at a telephoto end in the eighth embodiment.
  • FIG. 33 is an optical sectional view in a ninth embodiment of the present invention.
  • FIG. 34 is a diagram of aberrations at a wide-angle end in the ninth embodiment.
  • FIG. 35 is a diagram of aberrations in an intermediate zoom position in the ninth embodiment.
  • FIG. 36 is a diagram of aberrations at a telephoto end in the ninth embodiment.
  • FIG. 37 is a schematic diagram of a main part of a camera of the present invention.
  • the zoom lens system includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, and a rear unit including at least one lens unit in the stated order from an object side to an image side.
  • At least the second lens unit is moved.
  • the rear unit includes, for example, a third lens unit having positive refractive power or includes the third lens unit having positive refractive power and a fourth lens unit having positive refractive power in the stated order from the object side to the image side.
  • the rear unit includes the third lens unit having positive refractive power, the fourth lens unit having positive refractive power, and a fifth lens unit having positive refractive power in the stated order from the object side to the image side.
  • the rear unit may include four or more lens units.
  • FIG. 1 is a sectional view of a main part at a wide-angle end (short focal length end) of a zoom lens system according to a first embodiment (lens sectional view).
  • FIGS. 2 to 4 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end (long focal length end) in the zoom lens system according to the first embodiment, respectively.
  • FIG. 5 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a second embodiment.
  • FIGS. 6 to 8 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the second embodiment, respectively.
  • FIG. 9 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a third embodiment.
  • FIGS. 10 to 12 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the third embodiment, respectively.
  • FIG. 13 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a forth embodiment.
  • FIGS. 14 to 16 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the fourth embodiment, respectively.
  • FIG. 17 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a fifth embodiment.
  • FIGS. 18 to 20 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the fifth embodiment, respectively.
  • FIG. 21 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a sixth embodiment.
  • FIGS. 22 to 24 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the sixth embodiment, respectively.
  • FIG. 25 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a seventh embodiment.
  • FIGS. 26 to 28 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the seventh embodiment, respectively.
  • FIG. 29 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to an eighth embodiment.
  • FIGS. 30 to 32 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the eighth embodiment, respectively.
  • FIG. 33 is a sectional view of a lens main part at a wide-angle end of a zoom lens system according to a ninth embodiment.
  • FIGS. 34 to 36 are aberration diagrams at the wide-angle end, in an intermediate focal length, and at a telephoto end in the zoom lens system according to the ninth embodiment, respectively.
  • FIG. 37 is a schematic diagram of a main part of a camera including the zoom lens system according to the present invention.
  • the zoom lens system according to each of the embodiments is an image pickup lens system used in a camera such as a video camera or a digital camera.
  • a camera such as a video camera or a digital camera.
  • the left is an object side (front) and the right is an image side (rear).
  • the zoom lens system according to each of the embodiments is used as a projection lens of a projector, the left is equivalent to a screen and the right is equivalent to an image to be projected.
  • a first lens unit L 1 having positive refractive power, a second lens unit L 2 having negative refractive power, a third lens unit L 3 having positive refractive power, a fourth lens unit L 4 having positive refractive power, and a fifth lens unit L 5 having positive refractive power are illustrated.
  • a rear unit LR including at least one lens unit is illustrated.
  • an aperture stop SP (F number determining stop) is arranged between an object side vertex of a lens arranged on a most object side and included in the third lens unit L 3 and an intersection of a surface on the object side of the lens and an outer periphery of the lens.
  • the aperture stop SP is arranged on the object side of the third lens unit L 3 .
  • G denotes a glass block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filer, or the like.
  • IP denotes an image plane on which an image pickup surface of a solid-state image pickup element (photoelectric transducer) of a CCD sensor, a CMOS sensor, or the like is placed in an image pickup optical system of a video camera or a digital still camera.
  • a solid-state image pickup element photoelectric transducer
  • the image plane is equivalent to a film surface in an image pickup optical system of a silver-halide film camera.
  • d and g represent d-line and g-line, respectively.
  • ⁇ M and ⁇ S represent a meridional image plane and a sagittal image plane, respectively.
  • a lateral chromatic aberration is represented by the g-line.
  • Fno represents an F number and ⁇ represents a half field angle.
  • the wide-angle end and the telephoto end refer to zoom positions where a lens unit for zooming is located at both ends of a movable range on an optical axis in terms of a mechanism.
  • Arrows indicate moving loci of the lens units during zooming from the wide-angle end to the telephoto end.
  • the first lens unit L 1 moves to be located on the object side at the telephoto end compared with the wide-angle end.
  • the second lens unit L 2 moves to increase an interval between the first lens unit L 1 and the second lens unit L 2 .
  • the third lens unit L 3 moves to decrease an interval between the second lens unit L 2 and the third lens unit L 3 .
  • the zoom lens system according to each of the embodiments includes, in order from the object side to the image side, the first lens unit L 1 having positive refractive power, the second lens unit L 2 having negative refractive power, and the rear unit LR including at least one lens unit.
  • the second lens unit L 2 consists of two lenses, a small zoom lens system having a high zoom ratio and high optical performance is attained by using, for example, a material having a high refractive index made of translucent ceramics.
  • the second lens unit L 2 consists of a negative biconcave lens component or a negative meniscus lens having a convex shape facing toward the object side and a positive meniscus lens element having a convex shape facing toward the object side.
  • a material having a high refractive index is used for the negative lens component, whereby curvatures of lens surfaces are relaxed to reduce occurrence of aberrations such as coma and field curvature and a reduction in thickness of an optical element is realized.
  • At least one surface of the negative lens component of the second lens unit L 2 is formed in an aspherical shape.
  • the surface on the object side has the aspherical shape, the surface is formed in a shape for intensifying negative refractive power toward off-axis, whereby negative field curvature in the off-axis position is corrected.
  • the surface on the image plane side has the aspherical shape
  • the surface is formed in a shape in which negative optical power reduces toward off-axis in order to cancel the barrel-like distortion caused by the surface on the object side.
  • the aspherical surface may be formed by stacking a resin material (replica) on the base material.
  • the positive meniscus lens element in the second lens unit L 2 needs to be formed by a material more highly dispersed than the negative lens component in order to correct chromatic aberration in the second lens unit L 2 .
  • the optical glass tends to be more highly dispersed as a refractive index increases.
  • Single crystals and polycrystals of ceramics and oxides are relatively low-dispersed even if the refractive index is high. Therefore, a reduction in size of the entire system is realized while chromatic aberration is corrected by using those materials.
  • the optical glasses are distributed along several straight lines in a graph in which the ordinate indicates a refractive index to be larger upward and the abscissa indicates an Abbe number to be larger leftward (hereinafter referred to as “nd ⁇ d chart”).
  • the optical glass has a characteristic that, when the refractive index increases, the Abbe number decreases and the dispersion increases.
  • such a material is used as a material of at least one of the positive lens element and the negative lens component of the second lens unit L 2 .
  • N 2 n represent a refractive index of at least one material forming the negative lens component of the second lens unit L 2 with respect to d-line and ⁇ 2 n represents an Abbe number of the material, and N 2 p represents a refractive index of a material forming the positive lens element of the second lens unit L 2 with respect to d-line.
  • Abbe number is an Abbe number ( ⁇ d) of a material with reference to d-line represented by the following expression.
  • ⁇ d ( Nd ⁇ 1)/( NF ⁇ NC )
  • the conditional expression (1) specifies a relation between a refractive index with respect to d-line and an Abbe number of the material included in the negative lens component of the second lens unit L 2 .
  • the refractive index of the material included in the negative lens component decreases so that N 2 n ⁇ (9.3 ⁇ 10 ⁇ 5 ⁇ 2 n 2 ⁇ 1.70 ⁇ 10 ⁇ 2 ⁇ 2 n ) is smaller than the lower limit of the conditional expression (1), a movement amount of the second lens unit L 2 increases in order to obtain a sufficient zoom ratio since the refractive power is small, whereby the lens system increases in size.
  • the conditional expression (2) specifies an Abbe number in d-line of the material included in the negative lens component of the second lens unit L 2 .
  • the conditional expression (2) specifies an Abbe number in d-line of the material included in the negative lens component of the second lens unit L 2 .
  • the Abbe number is smaller than the lower limit of the conditional expression (2), a more highly dispersed material cannot be selected as a material of the positive lens element in order to correct chromatic aberration in the second lens unit L 2 .
  • the material included in the negative lens component is low-dispersed so that the Abbe number exceeds the upper limit of the conditional expression (2), the lateral chromatic aberration at the wide-angle end is undesirably excessively corrected.
  • the conditional expression (3) specifies an average refractive index of materials of the lenses forming the second lens unit L 2 .
  • the average refractive index is smaller than the lower limit of the conditional expression (3), curvatures of lens surfaces of the negative lens component and the positive lens element decrease, and high-order aberration occurs on the lens surfaces, whereby optical performance is deteriorated.
  • each of the lenses increases and the length on an optical axis of the entire second lens unit L 2 increases.
  • the effect of correcting a Petzval sum in a minus direction decreases and an image plane characteristic undesirably tilts to the negative side.
  • Numerical value ranges of the conditional expressions (2) and (3) are further desirably set as follows: 30 ⁇ 2n ⁇ 55 (2a) 2.00 ⁇ (N2n+N2p)/2 ⁇ 2.20 (3a)
  • the second lens unit can be formed by a small number of lenses while the second lens unit has a high zoom ratio and high optical performance. Consequently, a reduction in size of the zoom lens system is attained.
  • the zoom lens system having a high zoom ratio and high optical performance over the entire zoom range is obtained.
  • D 2 represents a distance from a surface on a most object side to a surface on a most image side of the second lens unit L 2 and fw represents a focal length of the zoom lens system at the wide-angle end.
  • the conditional expression (4) specifies the thickness on the optical axis of the second lens unit L 2 .
  • the thickness of the second lens unit L 2 reduces so that D 2 /fw is smaller than the lower limit of the conditional expression (4), the negative lens component and the positive lens element interfere with each other. Therefore, it is difficult to give a curvature of predetermined refractive power to the lens surfaces and satisfactorily perform aberration correction.
  • ⁇ 2P represents an Abbe number of the material forming the positive lens element of the second lens unit L 2 .
  • the conditional expression (5) specifies a relation between Abbe numbers of the material included in the negative lens component and the material forming the positive lens element of the second lens unit L 2 .
  • a ratio of the Abbe numbers is smaller than the lower limit of the conditional expression (5), lateral chromatic aberration at the wide-angle end is insufficiently corrected. Therefore, correcting the lateral chromatic aberration causes the thickness of the second lens unit L 2 to increase.
  • the ratio of the Abbe numbers is larger than the upper limit of the conditional expression (5), lateral chromatic aberration at the wide-angle end is excessively corrected.
  • f 2 n and f 2 p represent the focal lengths of the negative lens component and the positive lens element of the second lens unit L 2 , respectively.
  • the conditional expression (6) specifies a ratio of refractive powers (inverses of the focal lengths) of the negative lens component and the positive lens element of the second lens unit L 2 .
  • a front lens diameter (first lens unit L 1 ) increases. Therefore, it is difficult to reduce the size of the entire system.
  • ft represents the focal length of the zoom lens system at the telephoto end.
  • the conditional expression (7) relates to a zoom ratio of the entire system.
  • the conditional expression (7) clarifies zoom ranges in the embodiments and designates a range in which a high zoom ratio, high optical performance, and a reduction in size of the entire system can be most effectively attained when a predetermined material is used.
  • the zoom ratio depends on refractive powers of the lens units arranged for magnification, a moving range during zooming, and the like.
  • the conditional expressions (8) and (9) specify a range of an appropriate zooming action of the second lens unit L 2 and the third lens unit L 3 .
  • is smaller than the lower limit of the conditional expression (8) or
  • a zooming action of the third lens unit L 3 is so strong that it becomes difficult to correct aberrations and sensitivity during manufacturing undesirably increases when attempting to obtain a high zoom ratio.
  • f 2 represents the focal length of the second lens unit L 2 .
  • the conditional expression (10) specifies a ratio of the focal length of the second lens unit L 2 to the focal length of the entire system at the wide-angle end.
  • the refractive power of the second lens unit L 2 decreases so that f 2 /fw is smaller than the lower limit of the conditional expression (10)
  • a movement amount of the second lens unit L 2 increases in order to obtain a sufficient zoom ratio and the entire system increases in size.
  • the refractive power of the second lens unit L 2 increases so that f 2 /fw is larger than the upper limit of the conditional expression (10)
  • a thickness deviation ratio of the negative lens in the second lens unit L 2 increases. Therefore, it is difficult to manufacture the second lens unit L 2 .
  • the thickness of each of the lenses increases because a curvature of each of the lens surfaces is sharp, and hence the thickness of the entire second lens unit L 2 increases.
  • f 1 represents the focal length of the first lens unit L 1 .
  • the conditional expression (11) specifies a ratio of the focal lengths of the first lens unit L 1 and the second lens unit L 2 .
  • the ratio is smaller than the lower limit of the conditional expression (11) an F number at the telephoto end undesirably increases.
  • the ratio is larger than the upper limit of the conditional expression (11) the front lens diameter increases and the entire system undesirably increases in size.
  • Numerical value ranges of the conditional expressions (4) to (11) are more desirably set as follows: 0.78 ⁇ D 2/ fw ⁇ 1.10 (4a) 2.0 ⁇ 2 n/ ⁇ 2 p ⁇ 3.15 (5a) ⁇ 0.39 ⁇ f 2 n/f 2 p ⁇ 0.22 (6a) 5.8 ⁇ ft/fw ⁇ 9 (7a) 1.6 ⁇
  • the zoom lens system includes, in order from the object side to the image side, the first lens unit L 1 having positive refractive power, the second lens unit L 2 having negative refractive power, the third lens unit L 3 having positive refractive power, and the fourth lens unit L 4 having positive refractive power.
  • the first lens unit L 1 moves along a locus convex to the image side and the second lens unit L 2 moves along a locus convex to the image side.
  • the third lens unit L 3 moves toward the object side and performs main magnification and the fourth lens unit L 4 moves toward the object side and reduces (compensates) image plane fluctuation caused by the magnification.
  • the first lens unit L 1 moves toward the image side during zooming from the wide-angle end to a substantially intermediate position to reduce a distance between the aperture stop SP and the first lens unit L 1 , to thereby realize a reduction in the front lens diameter.
  • the first lens unit L 1 includes a composite optical element including, in order from the object side, a positive lens element (first optical element) (a refracting surface on the image side has larger positive power than a refracting surface on the object side) and an optical element (second optical element) joined to the positive lens element and having negative refractive power.
  • the second optical element is desirably made of a resin material.
  • the first lens unit L 1 also includes the composite optical element including the positive lens element and the optical element joined to the positive lens element and having negative refractive power in the third, fourth, fifth, sixth, and eighth embodiments described later.
  • the composite optical element includes a first optical element G 11 and a second optical element G 12 (or multiple second optical elements G 12 ) joined to the first optical element G 11 .
  • the first optical element G 11 and the second optical element (desirably, auxiliary lens made of resin) G 12 jointed to the first optical element G 11 satisfy a relation described below.
  • the thickness of the first optical element on an optical axis is three times or more (desirably, five times or more) as large as the thickness of the second optical element on an optical axis.
  • the thickness of the first optical element on the optical axis is desirably 100 times or less as large as the thickness of the second optical element on the optical axis.
  • An absolute value of the refractive power (inverse of focal length) of the first optical element is twice or more (desirably, 2.5 times or more) as large as an absolute value of the refractive power of the second optical element.
  • the absolute value of the refractive power (inverse of focal length) of the first optical element is 50 times or less (desirably, 40 times or less) as large as the absolute value of the refractive power of the second optical element.
  • the second lens unit L 2 includes, in order from the object side, a negative biconcave lens element and a positive meniscus lens element having a convex shape facing toward the object side.
  • a negative lens component of the second lens unit L 2 includes only the negative lens element.
  • a material such as ceramics, having a refractive index N 2 n of which is 1.97500 and an Abbe number ⁇ 2 n of which is 39.5, is used for the negative lens element. Because the material of the negative lens element has a high refractive index, if the lens surfaces have the same curvature, occurrence of aberrations can be suppressed even if the refractive power of the negative lens is increased. Therefore, it is easy to increase a zoom ratio, and if magnification is the same, the curvatures of the lens surfaces can be relaxed. This makes it easy to improve optical performance and reduce the thickness of the second lens unit L 2 .
  • This material (ceramics) has a higher refractive index than the general optical glass material but has a large Abbe number (small dispersion). Therefore, lateral chromatic aberration at the wide-angle end can be satisfactorily corrected.
  • a material such as k-PSFn214 (product name) of Sumita Optical Glass, Inc., having the refractive index N 2 p, 2.14352, and the Abbe number ⁇ 2 p, 17.8, is used for the positive lens element. Consequently, an increase in magnification in the positive lens element, improvement of optical performance, and a reduction in size of the entire system are realized.
  • a material having a high refractive index and high dispersion is used as a material of the positive lens element. Consequently, a reduction in size of the entire system and aberration correction are effectively performed.
  • the zooming action of the second lens unit L 2 is intensified and sharing amount of magnification of the other lens units is reduced to realize a zoom lens system having low eccentricity sensitivity.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • the fourth lens unit L 4 moves to the front side.
  • the lens unit that performs main magnification refers to a lens unit that has a largest value of a ratio of a change in imaging magnification for zooming from the wide-angle end to the telephoto end compared with all the other lens units.
  • a basic lens configuration including the number of lens units, signs of refractive powers of the lens units, and movement conditions of the lens units during zooming is the same as that in the first embodiment illustrated in FIG. 1 .
  • Optical elements (second optical elements) (desirably made of a resin material) having negative refractive power are arranged on the object side and the image side (or one of the object side and the image side) of the negative lens element (first optical element).
  • the optical elements having negative refractive power are joined to the negative lens element of the second lens unit L 2 .
  • the negative lens component of the second lens unit L 2 consists of the negative lens element (first optical element) and the second optical elements joined to the negative lens element.
  • An increase in magnification, improvement of optical performance, and a reduction in size of the entire system are realized by those materials as in the first embodiment.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in aspherical shape to satisfactorily correct coma at the telephoto end.
  • the aspherical surfaces are molded by using a resin material as a high-refractive material to thereby facilitate manufacturing. Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • a basic lens configuration including the number of lens units, signs of refractive powers of the lens units, and movement conditions of the lens units for zooming, is the same as that of the first embodiment illustrated in FIG. 1 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • a basic lens configuration including the number of lens units, signs of refractive powers of the lens units, and movement conditions of the lens units for zooming, is the same as that of the first embodiment illustrated in FIG. 1 .
  • the negative lens component of the second lens unit L 2 consists of only the negative lens element.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • a basic lens configuration including the number of lens units, signs of refractive powers of the lens units, and movement conditions of the lens units for zooming, is the same as that of the first embodiment illustrated in FIG. 1 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • a basic lens configuration including the number of lens units, signs of refractive powers of the lens units, and movement conditions of the lens units for zooming, is the same as that of the first embodiment illustrated in FIG. 1 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • An increase in magnification, improvement of optical performance, and a reduction in size of the entire system are realized by those materials as in the first embodiment.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • the seventh embodiment illustrated in FIG. 25 is a three-unit zoom lens system in which the entire system is formed by three lens units.
  • the zoom lens system includes, in order from the object side to the image side, the first lens unit L 1 having positive refractive power, the second lens unit L 2 having negative refractive power, and the third lens unit L 3 having positive refractive power.
  • the first lens unit L 1 moves along a locus convex to the image side.
  • the second lens unit L 2 moves along a locus convex to the image side to correct image plane fluctuation involved in magnification.
  • both surfaces of the negative lens component of the second lens unit L 2 are formed in an aspherical shape to satisfactorily correct field curvature and distortion. Further, both surfaces of the positive lens element of the second lens unit L 2 are also formed in an aspherical shape to satisfactorily correct coma at the telephoto end.
  • the third lens unit L 3 moves toward the object side to thereby perform main magnification.
  • the first lens unit L 1 moves toward the image side during zooming from the wide-angle end to the intermediate position to reduce a distance between the third lens unit L 3 and the aperture stop SP, to thereby realize a reduction in the front lens diameter.
  • the entire system includes the three lens units and the number of lenses of the lens units is a necessary minimum number, but oxide ceramics such as yttrium aluminium garnet is used for the negative lens of the second lens unit L 2 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • a high-refractive-index material such as KT crystal (KTaO3) is used for the positive lens element to realize a reduction in size of the entire system and improvement of optical performance by making use of the aspherical effect.
  • Focusing from an infinity object to a near distance object is performed by moving the second lens unit L 2 toward the front side.
  • the eighth embodiment illustrated in FIG. 29 is a five-unit zoom lens system in which the entire system is formed by five lens units.
  • the zoom lens system includes, in order from the object side to the image side, the first lens unit L 1 having positive refractive power, the second lens unit L 2 having negative refractive power, the third lens unit L 3 having positive refractive power, the fourth lens unit L 4 having positive refractive power, and the fifth lens unit L 5 having positive refractive power.
  • the first lens unit L 1 moves along a locus convex to the image side.
  • the second lens unit L 2 moves along a locus convex to the image side.
  • the third lens unit L 3 moves toward the object side to thereby perform main magnification.
  • the fourth lens unit L 4 moves toward the image side.
  • the fifth lens unit L 5 moves toward the object side to correct image plane fluctuation involved in magnification.
  • the first lens unit L 1 moves toward the image side during zooming from the wide-angle end to the intermediate position to thereby realize a reduction in the front lens diameter.
  • Both surfaces of the negative lens component of the second lens unit L 2 are formed in aspherical shape.
  • Oxide ceramics such as yttrium aluminium garnet is used for the negative lens element of the second lens unit L 2 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • a high-refractive-index material such as k-PSFn214 (product name) of Sumita Optical Glass, Inc. is used for the positive lens element to realize a reduction in size of the entire system and improvement of optical performance by making use of the aspherical effect.
  • Focusing from an infinity object to a near distance object is performed by moving the fifth lens unit L 5 toward the front side.
  • the ninth embodiment illustrated in FIG. 33 is a five-unit zoom lens system in which the entire system is formed by five lens units.
  • the zoom lens system includes, in order from the object side to the image side, the first lens unit L 1 having positive refractive power, the second lens unit L 2 having negative refractive power, the third lens unit L 3 having positive refractive power, the fourth lens unit L 4 having positive refractive power, and the fifth lens unit L 5 having positive refractive power.
  • the first lens unit L 1 moves toward the object side.
  • the second lens unit L 2 moves toward the image side to thereby perform main magnification.
  • the third lens unit L 3 moves toward the object side.
  • the fourth lens unit L 4 moves toward the image side.
  • the fifth lens unit L 5 moves toward the object side to correct image plane fluctuation involved in magnification.
  • the image-side surface of the negative lens component of the second lens unit L 2 is formed in aspherical shape.
  • Oxide ceramics such as yttrium aluminium garnet is used for the negative lens element of the second lens unit L 2 .
  • the negative lens component of the second lens unit L 2 includes only the negative lens element.
  • a high-refractive-index material such as k-PSFn214 (product name) of Sumita Optical Glass, Inc. is used for the positive lens element to realize a reduction in size of the entire system and improvement of optical performance by making use of the aspherical effect.
  • Focusing from an infinity object to a near distance object is performed by moving the fourth lens unit L 4 toward the front side.
  • a curvature radius of an i-th lens surface (i-th surface) in the stated order from the object side is indicated by ri.
  • An interval between the i-th surface and an (i+1)th surface is indicated by di.
  • a refractive index and an Abbe number with respect to d-line are indicated by ndi and ⁇ di, respectively.
  • two surfaces on the most image side are surfaces forming an optical block G.
  • a value of d 8 is minus.
  • a value of d 9 is minus. This is because the aperture stop SP and the lens surface on the most object side of the third lens unit L 3 are counted in the stated order from the object side.
  • a shape of the lens surface is represented as described below.
  • a position in an optical axis direction is represented as X
  • a position in a direction orthogonal to the optical axis is represented as H
  • a traveling direction of light is positive.
  • a paraxial curvature radius is represented as R
  • a conic coefficient is represented as K
  • aspherical coefficients are represented as A 4 , A 6 , A 8 , and A 10 , respectively.
  • the shape is represented by the following formula.
  • FIG. 37 An embodiment of a digital still camera in which the zoom lens system according to the present invention is used as a shooting optical system is described with reference to FIG. 37 .
  • the digital still camera includes a camera main body 20 and a shooting optical system 21 constituted by the zoom lens system described in any one of the first to ninth embodiments.
  • a solid-state image pickup element (photoelectric transducer) 22 such as a CCD sensor or a CMOS sensor is incorporated in the camera main body 20 and receives light of an object image formed by the shooting optical system 21 .
  • a memory 23 records information corresponding to the object image photoelectrically converted by the solid-state image pickup element 22 .
  • a finder 24 is constituted by a liquid crystal display panel or the like and is used for observing the object image formed on the solid-state image pickup element 22 .
  • the zoom lens system according to any one of the embodiments of the present invention is applied to a camera such as the digital still camera, whereby a small camera having high optical performance is realized.
  • the zoom lens system according to any one of the embodiments of the present invention can also be applied to a video camera, a TV camera, a silver-halide film camera, and the like.

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JP5463855B2 (ja) * 2009-04-24 2014-04-09 株式会社リコー ズームレンズおよびカメラ装置および携帯情報端末装置
JP5628572B2 (ja) * 2009-07-03 2014-11-19 パナソニック株式会社 ズームレンズ系、撮像装置及びカメラ
JP5562586B2 (ja) * 2009-07-10 2014-07-30 オリンパス株式会社 結像光学系及びそれを有する電子撮像装置
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JP5686644B2 (ja) * 2011-03-24 2015-03-18 キヤノン株式会社 ズームレンズ及びそれを有する撮像装置
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JP6039332B2 (ja) * 2012-09-21 2016-12-07 キヤノン株式会社 ズームレンズ及びそれを有する撮像装置
JP6268697B2 (ja) * 2012-10-23 2018-01-31 株式会社ニコン 変倍光学系、光学装置、変倍光学系の製造方法
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JP6056429B2 (ja) * 2012-12-03 2017-01-11 リコーイメージング株式会社 超広角レンズ系
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JP6608349B2 (ja) * 2016-12-09 2019-11-20 キヤノン株式会社 ズームレンズ及びそれを有する撮像装置
JP6598761B2 (ja) * 2016-12-09 2019-10-30 キヤノン株式会社 ズームレンズ及びそれを有する撮像装置
US10908400B2 (en) 2016-12-09 2021-02-02 Canon Kabushiki Kaisha Zoom lens, image pickup apparatus including the same, and control device for the same
JP6943265B2 (ja) * 2017-03-07 2021-09-29 株式会社ニコン 変倍光学系、光学装置
WO2018173585A1 (ja) * 2017-03-22 2018-09-27 ソニー株式会社 投射レンズおよび投影装置
JP7086579B2 (ja) * 2017-11-24 2022-06-20 キヤノン株式会社 ズームレンズ及び撮像装置
CN110244436B (zh) * 2019-06-29 2021-09-21 瑞声光学解决方案私人有限公司 摄像光学镜头
JP7270970B2 (ja) * 2019-07-11 2023-05-11 株式会社シグマ 防振機能を備えた変倍結像光学系
JP2021026087A (ja) * 2019-08-02 2021-02-22 キヤノン株式会社 ズームレンズ、画像投写装置、および、撮像装置

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